1. Field of the Invention
The present invention relates to an ion implantation device.
2. Description of the Related Art
In general, ion implantation devices are widely used in doping impurity such as boron, phosphorus, arsenic to a semiconductor wafer.
In such conventional ion implantation devices such as an ion implantation device of a medium current type, a predetermined ion, which is generated by an ion source, is selected by a mass-spectrometry magnet, and accelerated by an accelerating tube. Thereafter, the ion is focused by a quadruple lens and is scanned and irradiated on a processing material, for example a semiconductor wafer, which is arranged in a platen as being scanned in an X - Y direction by an X - Y scanning electrode.
In the above-structured ion implantation device, as such an ion source, there is frequently used an ion source of a hot-cathode type forming a plasma by discharging source gas, thereby generating ions. Moreover, since a high voltage is applied to the ion source, the ion source and a unit such as a power source for supplying power to the ion source are contained in a cylindrical member, which is normally called an enclosure, in order to be electrically isolated from the outside. Also, there is provided a box, which is called a gas box, in the enclosure. In the gas box, there is contained a gas cylinder for supplying source gas to the ion source.
Therefore, the space where the gas cylinder is provided is limited, so that a large-sized gas cylinder can not be used. The gas cylinder of about 0.35 l is normally used. Therefore, the term for which one gas cylinder can be used is normally about one week to one month though this depends on frequency in use of gas cylinder. Therefore, one gas cylinder must be exchanged for a new one by a week or a month.
Moreover, it takes much time to perform the exchange of the gas cylinder for new on and the adjustment after the exchange. Specifically, down time of one or two days is normally generated in accordance with the exchange of the gas cylinder, so that productivity is worsened.
Furthermore, the ion implantation device is normally in a clean room. Several workers must enter the clean room for a certain period of time to perform the exchange of the gas cylinder for a new one and the adjustment after the exchange. Since the human body becomes a source where dust is generated, it is desirable that the frequencies of which the workers enter the clean room be reduced as possible. Particularly, there is a tendency for the semiconductor device to be highly integrated recently, and it has been required that cleanness in the clean room be improved more than the conventional one. For this reason, necessity for reducing the frequencies of which the workers enter the clean room has been raised. Also, since the clean room has an extremely narrow room, it can be said that the exchange of the gas cylinder always involves danger in view of safety.